Re: [PATCH] scsi: libsas: Fix SMP IO deadlock during HA resume

[yangxingui <yangxingui@huawei.com>]

Hi John & Jason,

Kindly ping for review...

On 2026/8/26 11:28, Xingui Yang wrote:
> During sas_resume_ha() -> sas_drain_work(), ATA EH will trigger SMP IOs via
> sas_phy_reset() -> sas_smp_phy_control() for expander-attached ATA devices.
> Since ha->dev is RPM_RESUMING at that point, pm_runtime_get_sync() blocks
> waiting for the resume to finish, but the resume is blocked in
> sas_drain_work() waiting for the SMP IO — a deadlock.
> 
> Skip the PM get/put when SAS_HA_RESUMING is set. The hardware is already
> initialized by the LLDD resume callback before sas_resume_ha() runs, so no
> explicit resume is needed.
> 
> Only hisi_sas enables runtime PM among libsas LLDDs, so other drivers
> (pm8001, isci, aic94xx, mvsas) are unaffected.
> 
> Fixes: 0da7ca4c4fd9 ("scsi: libsas: Resume host while sending SMP I/Os")
> Signed-off-by: Xingui Yang <yangxingui@huawei.com>
> ---
>   drivers/scsi/libsas/sas_expander.c | 16 +++++++++++++---
>   1 file changed, 13 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/scsi/libsas/sas_expander.c b/drivers/scsi/libsas/sas_expander.c
> index 811c9eb4fef1..77ae2ae7b2c4 100644
> --- a/drivers/scsi/libsas/sas_expander.c
> +++ b/drivers/scsi/libsas/sas_expander.c
> @@ -61,8 +61,17 @@ static int smp_execute_task_sg(struct domain_device *dev,
>   	struct sas_internal *i =
>   		to_sas_internal(dev->port->ha->shost->transportt);
>   	struct sas_ha_struct *ha = dev->port->ha;
> -
> -	pm_runtime_get_sync(ha->dev);
> +	bool skip_pm = test_bit(SAS_HA_RESUMING, &ha->state);
> +
> +	/*
> +	 * Skip PM get/put during HA resume to avoid deadlock: the host is
> +	 * RPM_RESUMING and the drain waits for this SMP IO to finish, but
> +	 * pm_runtime_get_sync() would block on RPM_RESUMING. Safe because
> +	 * hardware is already initialized by the LLDD before call
> +	 * sas_resume_ha().
> +	 */
> +	if (!skip_pm)
> +		pm_runtime_get_sync(ha->dev);
>   	mutex_lock(&dev->ex_dev.cmd_mutex);
>   	for (retry = 0; retry < 3; retry++) {
>   		if (test_bit(SAS_DEV_GONE, &dev->state)) {
> @@ -135,7 +144,8 @@ static int smp_execute_task_sg(struct domain_device *dev,
>   		}
>   	}
>   	mutex_unlock(&dev->ex_dev.cmd_mutex);
> -	pm_runtime_put_sync(ha->dev);
> +	if (!skip_pm)
> +		pm_runtime_put_sync(ha->dev);
>   
>   	BUG_ON(retry == 3 && task != NULL);
>   	sas_free_task(task);
>